This invention relates generally to methods of identifying implanted medical devices and implantable leadwires and systems. More specifically, this invention relates to radio frequency identification (RFID) tags for use with medical devices and lead systems implanted in a patient.
There are known in the art various methods for identifying implanted medical devices. One such method is the use of X-ray identification tags encapsulated within header blocks of pacemakers or implantable cardioverter defibrillators (ICD). Such X-ray identification tags can be read on an X-ray of the implanted device and provide information to the physician. The information so provided is limited due to space and typically includes only the manufacturer and model number of the implanted device.
It would be beneficial if physicians were able to obtain additional information about an implanted device and/or a patient from an implanted identification tag. Such beneficial information includes, in addition to the manufacturer and model number of the device, the serial number of the device, the treating physician's name and contact information and, if authorized by the patient, the patient's name, contact information, medical condition and treatment, and other relevant information concerning device program parameters and the like.
Currently, most active implantable medical device (AIMD) patients carry some sort of identification. This could be in the form of a card carried in the wallet or an ID bracelet indicating, for example, that they are a pacemaker wearer of a certain model and serial number. However, such forms of identification are often not reliable. It is quite common for an elderly patient to be presented at the emergency room (ER) of a hospital without their wallet and without wearing any type of a bracelet. In addition, there have been a number of situations where the patient (due to dementia or Alzheimer's, etc.) cannot clearly state that he or she even has a pacemaker.
Often times the ER physician will palpitate the patient's chest and feel that there is an implanted device present. If the patient is comatose, has low blood pressure, or is in another form of cardiac distress, this presents a serious dilemma for the ER. At this moment in time, all that the ER knows is that the patient has some sort of an AIMD implant in his or her chest. It could be a pacemaker, a cardioverter defibrillator, or even a vagus nerve stimulator or deep brain stimulator. What happens next is both laborious and time consuming. The ER physician will have various manufacturers' external telemetry programmers transported from the hospital cardiology laboratory down to the ER. ER personnel will then try to interrogate the implantable medical device to see if they can determine what it is. For example, they might first try to use a Medtronic programmer to see if it is a Medtronic pacemaker. Then they might try a St. Jude, a Guidant, an ELA, a Biotronik or one of a number of other programmers that are present. If none of those programmers work, then the ER physician has to consider that it may be a neurostimulator and perhaps go get a Cyberonics or Neuropace programmer.
It would be a great advantage and potentially life saving if the ER physician could very quickly identify the type of implant and model number. In certain cases, for example, with a pacemaker patient who is in cardiac distress, with an external programmer they could boost the pacemaker output voltage to properly recapture the heart, obtain a regular sinus rhythm and stabilize blood pressure. All of the lost time running around to find the right programmer, however, generally precludes this. Accordingly, there is a need for a way to rapidly identify the type and model number of an active implantable medical device so that the proper external programmer for it can be rapidly identified and obtained.
It is also important to note that leadwire systems generally remain in the human body much longer than the active implantable medical device itself. For example, in the case of a cardiac pacemaker, the cardiac pacemaker batteries tend to last for 5 to 7 years. It is a very difficult surgical procedure to actually remove leads from the heart once they are implanted. This is because the distal TIP of the leadwires tend to become embedded and overgrown by myocardial tissue. It often takes very complex surgical procedures, including open heart surgery, to remove such leadwire systems. When a pacemaker is replaced, the pectoral pocket is simply reopened and a new pacemaker is plugged into the existing leadwire. However, it is also quite common for leadwires to fail for various reasons. They could fail due to breakdown of electrical insulation or they could migrate to an improper position within the heart. In this case, the physician normally snips the leadwires off and abandons them and then installs new leadwires in parallel with the old abandoned leads.
Abandoned leadwires can be quite a problem during certain medical diagnostic procedures, such as MRI. It has been demonstrated in the literature that such leadwires can greatly overheat due to the powerful magnetic fields induced during MRI. Accordingly, it is important that there be a way of identifying abandoned leads and the lead type. Accordingly, there is a need to identify such abandoned leadwires to an Emergency Room physician or other medical practitioner who may contemplate performing a medical diagnostic procedure on the patient such as MRI. This is in addition to the need to also identify the make and model number of the active implantable medical device.
It is also important to note that certain leadwire systems are evolving to be compatible with a specific type of medical diagnostic procedure. For example, U.S. patent application Ser. Nos. 11/558,349 and 11/423,073, both of which being incorporated by reference in full herein, disclose the use of tank filters placed in series with leadwires or circuits of active medical devices to enhance their MRI compatibility. MRI systems vary in static field strength from 0.5 Tesla all the way above 10 Tesla. A very popular MRI system, for example, operates at 3 Tesla and has a pulse RF frequency of 128 MHz. There are specific certain leadwire systems that are evolving in the marketplace that would be compatible with only this type of MRI system. In other words, it would be dangerous for a patient with a leadwire designed for 3 Tesla to be exposed to a 1.5 Tesla system. Thus, there is also a need to identify such leadwire systems to Emergency Room and other medical personnel when necessary. For example, a patient that has a leadwire system that has been specifically designed for use with a 3 Tesla MRI system may have several pacemaker replacements over the years.
It is already well known in the prior art that RFID tag implants can be used for animals, for example, for pet tracking. It is also used in the livestock industry. For example, RFID tags can be placed in cattle to identify them and track certain information. There is also approval from the FDA for an injectable RFID tag into a human. A problem with this has to do with the fact that none of the current RFID tags have been designed to have long term reliability and biocompatibility within the body fluid environment.
Other general methods, none of which are specific to AIMDs, include encapsulating an RFID tag in plastic or placing the RFID tag in a plastic or glass tube with an epoxy infill. However, as will be discussed more fully below, none of these materials provide a truly hermetic seal against body fluids.
Accordingly, there is a need for an improved medical identification tag that can store additional information about an implanted device and/or a patient, without unduly increasing the size of the identification tag or jeopardizing the operation of the implanted device or the health of the patient, while providing a better hermetic seal.
The present invention meets these needs by providing an RFID tag that can be enclosed within an AIMD, introduced into a patient's body adjacent to an AIMD, or attached to or otherwise associated with a leadwire system. The RFID tag of the present invention is capable of storing information about the medical device, the leadwire system, the physician, and the patient, as described above.